The goals of a properly designed compound bow include the use of an eccentric wheel as disclosed in the U.S. Pat. No. 3,486,495, to Allen, issued Dec. 30, 1969. With this type of bow, eccentrically mounted wheels are positioned at the ends of the bow limb. During the draw by the archer, the wheels move over center to decrease the holding force at full draw while storing the required energy for the propulsion of the released arrow. Allen disclosed round wheels but recent developments have utilized what is referred to as high energy wheels with contours which store greater energy during the draw and gain in shooting performance. Reference is made also to a U.S. Pat. No. 4,340,925, to Caldwell, issued July 20, 1982.
Another goal in the design of bows which utilize high performance wheels is the elimination of the need for cable guards for the purpose of cable clearance for arrows and fletching during the release phase.
A further goal is the elimination of the torquing or twisting of the bow limb as they are being flexed during the draw and the release.
Because of the additional energy being stored with the use of the high performance bow limb wheels as the bow is drawn and because of the amount of tension being transferred from the string cable to the anchor cable, it is not possible to achieve the above outlined goals with the present state of the art bows as exemplified in the Allen patent above identified or in the U.S. Pat. No. 4,338,910, to Darlington, issued July 13, 1982.
It is therefore an object of the present invention to provide a high energy bow design which achieves as nearly as possible the goals set forth above. These goals are achieved as briefly set forth below.
First, the anchor end of the anchor cables are located as far as possible toward the center of the bow limb in relation to outermost secondary pulley groove as distinguished from the main drawstring pulley as will be explained in the detailed description.
Second, as is known in bow design, the arrow and fletching clearance is maintained by positioning the secondary pulley groove offset from the true center of the bow through the initial portion of the draw. This also offsets or balances the initial tension of the drawstring which is far greater at that phase of the draw.
Third, form the groove in the secondary pulley so that it moves transversely across the pulley as it is rotated in the draw so the groove is as close as possible to the groove in the primary pulley as the bow is drawn to its peak load.
Fourth, through the remainder of the draw, the cable tension will be as close to the center line of the bow limbs as possible.
An additional object is the provision of a camming sheave groove to insure transition of a cable sheave during the draw.
A further object and feature is the design of the pulley to provide axial and radial clearance on the composite pulley so the cable end anchor point can be as near as possible to the center of each bow limb to concentrate the forces at the center of the limb.
Other objects and features of the invention will be evident in the following description and claims in which the invention is described together with details to enable persons skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.